Bottom Line:
How these integral proteins are assembled in the outer membrane had been unclear.In eukaryotes, Omp85 is present in the mitochondrial outer membrane.The gene encoding Omp85 is essential for cell viability in yeast, and conditional omp85 mutants have defects that arise from compromised insertion of integral proteins like voltage-dependent anion channel (VDAC) and components of the translocase in the outer membrane of mitochondria (TOM) complex into the mitochondrial outer membrane.

Affiliation: Russell Grimwade School of Biochemistry and Molecular Biology, University of Melbourne, Melbourne 3010, Australia.

ABSTRACTIntegral proteins in the outer membrane of mitochondria control all aspects of organelle biogenesis, being required for protein import, mitochondrial fission, and, in metazoans, mitochondrial aspects of programmed cell death. How these integral proteins are assembled in the outer membrane had been unclear. In bacteria, Omp85 is an essential component of the protein insertion machinery, and we show that members of the Omp85 protein family are also found in eukaryotes ranging from plants to humans. In eukaryotes, Omp85 is present in the mitochondrial outer membrane. The gene encoding Omp85 is essential for cell viability in yeast, and conditional omp85 mutants have defects that arise from compromised insertion of integral proteins like voltage-dependent anion channel (VDAC) and components of the translocase in the outer membrane of mitochondria (TOM) complex into the mitochondrial outer membrane.

fig1: The Omp85 family. (A) Bootstrap support for eukaryote and other major nodes shown using weighted neighbor joining (top) and Fitch-Margoliash (bottom). Dashes indicate values <50%. (B) Sequence conservation between selected Omp85 family members and the consensus sequence derived with the conserved domain architecture retrieval tool (CDART; Geer et al., 2002). The most highly conserved section of the consensus sequence (shaded) includes the region corresponding to two predicted β-strands (designated by arrows), the least conserved (lower case) a predicted interstrand loop.

Mentions:
Iterative BLAST analyses revealed homologues of Omp85 in diverse species of proteobacteria and in spirochetes such as Borrelia burgdorferi and Treponema pallidum. In addition, Omp85 is encoded in the genomes of phylogenetically distinct gram-positive bacteria that maintain an outer membrane to assist their growth in extreme environments, e.g., the heat- and radiation-resistant Deinococcus radiodurans and the hyperthermophile Thermatoga maritime (Fig. 1 A). Omp85 consists of two domains, an NH2-terminal α/β periplasmic domain that includes the sequences required for secretion from the bacteria (Manning et al., 1998; Genevrois et al., 2003; Voulhoux et al., 2003) and a COOH-terminal “surface antigen” domain, so called because antibodies against this domain are protective against Haemophilus influenzae infection in animal models (Loosmore et al., 1997).

fig1: The Omp85 family. (A) Bootstrap support for eukaryote and other major nodes shown using weighted neighbor joining (top) and Fitch-Margoliash (bottom). Dashes indicate values <50%. (B) Sequence conservation between selected Omp85 family members and the consensus sequence derived with the conserved domain architecture retrieval tool (CDART; Geer et al., 2002). The most highly conserved section of the consensus sequence (shaded) includes the region corresponding to two predicted β-strands (designated by arrows), the least conserved (lower case) a predicted interstrand loop.

Mentions:
Iterative BLAST analyses revealed homologues of Omp85 in diverse species of proteobacteria and in spirochetes such as Borrelia burgdorferi and Treponema pallidum. In addition, Omp85 is encoded in the genomes of phylogenetically distinct gram-positive bacteria that maintain an outer membrane to assist their growth in extreme environments, e.g., the heat- and radiation-resistant Deinococcus radiodurans and the hyperthermophile Thermatoga maritime (Fig. 1 A). Omp85 consists of two domains, an NH2-terminal α/β periplasmic domain that includes the sequences required for secretion from the bacteria (Manning et al., 1998; Genevrois et al., 2003; Voulhoux et al., 2003) and a COOH-terminal “surface antigen” domain, so called because antibodies against this domain are protective against Haemophilus influenzae infection in animal models (Loosmore et al., 1997).

Bottom Line:
How these integral proteins are assembled in the outer membrane had been unclear.In eukaryotes, Omp85 is present in the mitochondrial outer membrane.The gene encoding Omp85 is essential for cell viability in yeast, and conditional omp85 mutants have defects that arise from compromised insertion of integral proteins like voltage-dependent anion channel (VDAC) and components of the translocase in the outer membrane of mitochondria (TOM) complex into the mitochondrial outer membrane.

Affiliation:
Russell Grimwade School of Biochemistry and Molecular Biology, University of Melbourne, Melbourne 3010, Australia.

ABSTRACTIntegral proteins in the outer membrane of mitochondria control all aspects of organelle biogenesis, being required for protein import, mitochondrial fission, and, in metazoans, mitochondrial aspects of programmed cell death. How these integral proteins are assembled in the outer membrane had been unclear. In bacteria, Omp85 is an essential component of the protein insertion machinery, and we show that members of the Omp85 protein family are also found in eukaryotes ranging from plants to humans. In eukaryotes, Omp85 is present in the mitochondrial outer membrane. The gene encoding Omp85 is essential for cell viability in yeast, and conditional omp85 mutants have defects that arise from compromised insertion of integral proteins like voltage-dependent anion channel (VDAC) and components of the translocase in the outer membrane of mitochondria (TOM) complex into the mitochondrial outer membrane.